DESCRIPTION: This study is examining the feasibility of flood risk management alternatives to address flooding issues within the Township of Denville. Denville is a municipality located within Morris County, New Jersey which is approximately 25 miles northwest of Newark. The study is focused on the central part of Denville, which is subject to fluvial flooding from the Rockaway River and Den Brook. Township residents and businesses have suffered extensive losses and damage from multiple flooding events in recent decades, including Hurricane Irene in August 2011 and Tropical Strom Ida in September 2021. An integrated feasibility report and environmental assessment will document the analysis and conclusions of the study.
AUTHORIZATION: This study is being conducted under Section 205 of the Continuing Authorities Program (CAP), which does not require individual study authorization.
STATUS: As a part of this study, which is an iterative process, the Project Delivery Team (PDT) has analyzed several different flood risk management alternatives. Throughout the process the PDT has coordinated their work with the New Jersey Department of Environmental Protection (NJDEP), who is the non-Federal sponsor, and the Township of Denville, who is a stakeholder on the project. Alternatives studied to date have included various structural measures such as floodwalls with closure gates, floodwalls in combination with road raisings, and diversion culverts. None of these structural alternatives analyzed were found to be economically justified so they could not move forward.
In addition to the structural alternatives the PDT has also analyzed nonstructural measures such as elevations, wet floodproofing, and dry floodproofing. The nonstructural analysis conducted by the PDT identified multiple groups or clusters of structures within the study area that were economically justified which indicates the benefits outweighed the costs. On November 20th, 2020 the PDT briefed our higher headquarters, USACE North Atlantic Division (NAD), at a Tentatively Selected Plan milestone in which approval was given to advance the nonstructural plan and complete a draft integrated feasibility report and environmental assessment for public release.
As the PDT was preparing the draft report for the first step in our internal review process discrepancies were identified in the nonstructural costs which prompted discussions with NAD. In coordination with NAD a decision was made to involve a subject matter expert within USACE to refine and detail the nonstructural costs. Detailed non-structural costs have been completed and the team is in the process of updating the economics. Once the economics are updated the team will re-evaluate the TSP for any changes and discuss with and coordinate with NJDEP, Denville Township, and NAD before the draft feasibility report can begin internal reviews. NAN received concurrence from NAD on the revised schedule and path forward. NAN/NAB is currently revising the Feasibility Report based on comments received by NAD on 8 NOV 2021 for DQC February 2022.
ESTIMATED STUDY COSTS & SCHEDULE: To date the study has received $700,000 in Federal funding, $100,000 of which was to prepare the Federal Interest Determination (FID) and Project Management Plan (PMP), with the remaining $600,000 in Federal funding being matched by the receipt of $600,000 in non-Federal funding to complete the Feasibility Study.
The schedule calls for the report to be released to the public in early March 2022 with a public meeting to occur during the 30-day public review period. Under this revised schedule a final report would be approved in late November 2022.
Bethany M. McClanahan P.E., CFM, ENV SP, WEDG
P: (917) 790-8426
U.S. Army Corps of Engineers, New York District
Programs and Project Management Division
26 Federal Plaza
New York, NY 10278